Memory of entrance-channel deformation for fast-fission

Fission fragment anisotropies following fusion of 34S with 168Er have been measured for energies at which a substantial fraction of fission results from angular momenta where the fission barrier height is less than the temperature. Here, transition state model calculations were found to be larger than the measured anisotropies. This result contrasts with data for 19F+208Pb, where the transition state model underestimated the measured anisotropies. Both observations can be explained qualitatively assuming that high angular momentum events fission with some memory of the entrance-channel K-distribution, which is narrow for the spherical 208Pb target nucleus, and broad for the deformed 168Er.